Drive system for strip accumulator

ABSTRACT

A drive system for roll cages in a strip accumulator of the type wherein the strip material is accumulated by being coiled into two substantially concentric sets of convolutions- an outer set and an inner set- connected by a free reverse loop which orbits between the sets of convolutions, the sets of convolutions being formed against expansible roll cages which support and guide the strip. The invention provides improved drive means for positioning the individual rolls making up the inner and outer roll cages, including sets of radially disposed coaxial drive shafts mounting the rollers for independent movement in opposite directions, the drive shafts for the rolls in the inner roll cage being operatively connected to a first ring gear drive means, with the drive shafts for the outer roll cages operatively connected to a second ring gear drive means, the drive system also including drivebelts associated with the rollers in the outer roll cage to implement the coiling of the strip, together with means for enclosing and protecting the coaxial drive shafts and their related mechanism.

United States Patent [72] inventor Alhed 0. Irltaehe Primary Examiner-George F. Mautz Hamilton, Ohio Assistant Examiner-Edward J. McCarthy [2!] Appl. No. 53,089 Attorney-Melville, Strasser, Foster & Hofiman [22] Filed July 8,1970 [45] Patented M21, 1971 73 d A 5...] (3 m ABSTRACT: A drive system for roll cages in a strip accumula- Mlddletewn,0l\lo tor of the type wherein the strip material is accumulated by being coiled into two substantially concentric sets of convolutions-an outer set and an inner set-connected by a free [54] DRIVE SYSTEM FOR STRIP ACCUMULATOR reverse loop which orbits between the sets of convolutions, 15 l l the sets of convolutions being formed against expansible roll [52] SJ-L 242/55 cages which support and guide the strip. The invention pro- 242/5519 vides improved drive means for positioning the individual rolls [5|] In. an 49/00 making up the inner and outer roll cages, including sets of 865' 51/22 radially disposed coaxial drive shafts mounting the rollers for 50 Field 0! Search 242/55 mmmm in 5118' 55.19 R 5511 550 4104 4707 4712' for the rolls in the inner roll cage being operatively connected to a first ring gear drive means, with the drive shafts for the [56] Ielerelces Cited outer roll cages operatively connected to a second ring gear UNITED STATES p drive means, the drive system also including drivebelts associated with the rollers in the outer roll cage to implement g E the coiling of the strip, together with means for enclosing and 3 91967 z 24'2/55 protecting the coaxial drive shafts and their related 3.506.210 4/1910 um" 242/55 mechamm' w n 41 4;, i =9 1 i E F WA I I, "41

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INVENTOR/S ALFRED GHQ/725045,

PATENTED M21 B-Il SHEET 1 OF 2 lzilllllllll! I BY v %adda, 504% M ATTORNEYS PATENTED M21 87! 3528 7 SHEET 2 OF '2 INVENTO R/S ALFRED 0. Fwrzscue.

m Yam, 2%, M/ K ATTOR N EYS DRIVE SYSTEM FOR STRIP ACCUMULATOR BACKGROUND OF THE INVENTION 1 In accordance with the teachings of this patent, the accumulator comprises a supporting'structure mounting a centrally .disposed circular inner cage of rollers around which an inner set of convolutions of the strip material is accumulated. Spaced outward from, and preferably concentric with, the central cage of rollers is a second cage of rollers adapted to contain and form an outer set of convolutions. The basic operating principle of the invention resides in the formation of a free reverse loop of strip which orbits in a space between the inner and outer roll cages to form two sets of convolutions each having the same number of turns at any given time during either feeding or delivery. Thus, strip from a decoiler or from a preceding processing line is fed into the accumulating device by a set of driven feed rollers or other drive means positioned to feed the strip in essentially tangential relation to the outer roll cage, the strip being fed to the inside of the rollers making up the outer cage. If it is-assumed that the initial direction of feed is in a counterclockwise direction, a free reverse loop is made in the strip before the first outer convolution is completed, i.e., the direction of the strip is reversed and a clockwise winding is begun around the inner roll cage. For discharge of strip from the accumulating device, the leading end of the strip is passed around a roll forming a part of the inner roll cage and then around an angularly disposed exit roll at the center of the device from which the strip is fed to a processing line or the like. Once the strip has been threaded through'the device'in the manner described, strip will be accumulated by feeding it into the device at a greater lineal rate than it is being withdrawn, such feeding movement causing the free reverse loop to move in an orbital path between the inner and outer sets of convolutions. A characteristic of the device is a numerical balance between the inner and outer sets of convolutions. For each convolution of strip added to the outer set of convolutions during accumulation, a convolution will also be added to the inner set by the orbiting reverse. loop.

Conversely, when strip is withdrawn from the device, the orbiting loop changes its direction of movement and for each convolution withdrawn from the inner set, a proportional length of strip will be withdrawn from the outer set and the numerical balance between the sets of convolutions will remain the same. The feeding of the strip is facilitated by mounting the rollers making up the outer roll cage for limited movement in a substantially radial path, thereby effectively permitting the diameter of the outer roll cage to increase as additional convolutions are added to the outer set. Similarly, the rollers in the inner roll cage may also be movably mounted, being urged radially outwardly so that, as the innermost convolutions are removed the inner roll cage will grow in diameter to prevent collapsing of the remaining convolutions which, in turn, prevents slippage between the convolutions.

The present invention provides a simplified and reliable mechanism for moving the expandable roll cages, the mechanism being of compact construction which is easy to assemble and maintain, and which is protected from external damage, dirt and grime.

RESUME OF THE INVENTION The present invention provides compact drive mechanism for the positioning of the rollers making up the inner and outer roll cages of a strip, accumulator, the mechanism comprising a series of drive units adapted to be radially disposed with respect to the center of the accumulator, each drive unit incorporating means for independently positioning one of the rollers in the inner roll cage' and a corresponding roller in the outer roll cage, the drive means including concentric drive shafts one of which is operatively connected to the roller in the outer roll cage, the other shaft being operatively connected to the corresponding roller in the inner roll cage, the shafts each being connected to a separate ring gear, the arrangement being such that the drive shafts of each of the radially disposed drive units are connected to and driven by the ring gears.

Preferably the drive units are mounted in opposing pairs, i.e one at each end of the rollers, so that the rollers will be stabilized as the roll cages expand and contract. Motive power for each of the ring gears is provided by one or more synchronized drive motors operatively connected to the ring gears either directly or through the intermediary of one of the drive shafts of the drive units themselves. In the latter event, the drive shaft serves both to move the roller to which it is operatively connected as well as provides motive power for the associated ring; gear which, in turn, drives the corresponding shafts of the remaining drive units.

Each of the drive units is adapted to be enclosed in a protective housing, the surface of the-housing facing the rollers having an elongated slot through which the axles of the rollers .project forconnection to their respective drive shafts, the

elongated slotbeing provided with'a flexible closurein the form of a pair of normally edge-abutting members which are compressible by the axles of the rollers, whereby the slots are effectively sealed against dirt and grime which mightotherwise enter the housing and contaminate the drive mechanism.

Theinvention also contemplates the provision of means for rotating the rollers making up the outer roll cage to facilitate the coiling of the strip, such means comprising coacting sets of drive belts and drive belt mounting means, including. prime movers, arranged to synchronously drive a series of adjoining rollers, the drive belt mounting means being adapted to move with the rollers in the outer cage as it expands and contracts.

DESCRIPTION OF THE DRAWINGS FIG. I is a diagrammatic vertical sectional view of an accumulator in accordance with the invention, the view being taken along the line 1-1 of FIG. 3.

FIG. 2 is anenlarged fragmentary sectional view of a drive unit taken along the line 2-2 of FIG. 1.

FIG. 3 is a vertically sectional view taken along the line 3- 3 of FIG. 1.

FIG. 4 is an enlarged vertical sectional view taken along the line 4-4 of FIG. 3 illustrating the manner in which the inner end of the concentric drive shafts are operatively connected to the ring gears.

FIG. 5 is an enlarged fragmentary elevational view illustrating drive means for driving the outer ring gear.

FIG.'6. is a fragmentary elevational view similar to FIG. 3 illustrating a modification wherein the drive shafts of corresponding drive units at the opposite ends of the rollers are connected to a common prime mover.

FIG. 7 is an enlarged fragmentary sectional view taken along the line7-7 of FIG. 6 illustrating the sealing of the drive unit housing against dirt and grime.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. I of the drawings, the accumulating device, which is indicated generally at 1, comprises a supporting structure 2 mounting a radially disposed series of drive units 3 each of which mounts an inner roller 4 and an outer roller 5. Collectively the inner rollers'4 define an inner roll cage, indicated generally at 6, whereas the outer rollers 5 collectively define an outer roll cage, indicated generally at 7. As will be apparent from FIGS. 3 and 6, each of the inner and outer rollers 4 and 5 is operatively connected at one end to the drive unit 3 and-at its opposite end to a corresponding drive unit 3a, the arrangement being such that the opposite ends of the rollers will be moved in unison, as will be explained more fully hereinafter. It will be understood, however, that the sets of drive units 3 and 3a will be essentially identical.

Referring again .to FIG. 1, a strip-feeding device 8 which includes a pair of driven feed rolls 9, is arranged to deliver a length of strip 10 into the accumulator in substantially tangential relation to the outer roll cage 7; and to this end adjustment means 11 may be provided to adjust the position of the stripfeeding device 8 relative to the outer roll cage. As the strip is fed into the device, it moves in a counterclockwise direction on the inside of the outer rollers and is characterized by a reverse loop l0a which reverses the direction of travel of the strip so that it passes around the inner rollers 4 in a clockwise direction. The strip is withdrawn from the device by being threaded inwardly around a series of guide rollers 12 which direct the strip into contact with a payoff roll or other payoff means, indicated diagrammatically by the arbor 13, which will mount a payoff roll or the like (not shown) which is preferably cylindrical in configuration with its axis inclined from the axis of rotation of the strip at an angle sufficient to provide clearance for the exiting strip beyond the ends of the rollers. To this end, it is preferred that the series of rollers 12 be mounted on a common support for joint movement. For example, the series of rollers 12 may be moved in unison by the drive unit 3b, in which event the drive units 3c, 3d, and 3e do not mount inner rollers 4. The purpose of such arrangement is to maintain the strip in proper alignment to be withdrawn from the device.

Strip removal is normally controlled either by driven exit rolls located beyond the device or by tension exerted by a processing line or the like which follows the accumulator. In either event, the inner set of convolutions rotates in response to tension on the innermost convolution from an internal or external tension-applying device. As strip is fed into the device, it will be evident that the reverse loop a will travel in a counterclockwise direction, effectively orbiting between the inner and outer roll cages. In so doing, convolutions of strip are concurrently built-up on both the inner and outer roll cages. Conversely, if the input of strip is stopped, but the output continues strip will be withdrawn from the'convolutions surrounding the inner roll cage, and such withdrawing movement will cause the reverse loop 10a to move in a clockwise direction such that strip from the outer set of convolutions supported by the outer roll cage will be transferred to the inner roll cage, and the numerical balance in the number of convolutions in each set maintained. It will be understood, of course, that strip may be simultaneously fed and discharged from the accumulator, the relative input and output speeds determining whether the number of convolutions will be built up or reduced in number. It should be further understood that in the foregoing description, the terms clockwise and counterclockwise are used in a relative sense, it being evident that strip could be fed into contact with the outer roll cage in a clockwise direction, in which event it would be wound around the inner roll cage in a counterclockwise direction.

In accordance with the present invention, mechanism is provided to expand the rollers in the outer roll cage outwardly as the outer set of convolutions builds up; and similarly, the inner roll cage will be expanded outwardly as the innermost convolutions are removed, the objective of the radially movable roll baskets being to stabilize the sets of convolutions and prevent unnecessary slippage between adjacent convolutions during coiling and decoiling. To this end, the rollers making up the outer roll cage are mounted for joint inward or outward movement, as are the rollers making up the inner roll cage, but the rollers in the outer roll cage may be jointly moved independently ofjoint movement of the rolls making up the inner roll cage. Their movement is controlled by the drive means now to be described.

As possibly best seen in FIG. 2, each of the drive units 3 comprises a first drive shaft 14 rotatably journaled at its inner end in a supporting bearing 15, and at its outer end in a supporting bearing 16. Toward its inner end the shaft 14 mounts a beveled pinion 17 the teeth of which engage the teeth of a first ring gear l8 rotatably mounted on the supporting structure 2. Toward its outer end the first drive shaft 14 is enlarged and defines a threaded portion 14a in threaded engagement with the threaded end portion 19 of a mounting sleeve 20 which surrounds the drive shaft and, at its opposite end mounts one end of an outer roller 5, the roller having an axle 21 by means of which it is operatively connected to the mounting sleeve.

A hollow second drive shaft 22 surrounds the portion of the first drive shaft intermediate the pinion l7 and the threaded portion 14a, the hollow shaft 22 being mounted on bearings 23 and 24 for rotation relative to the first shaft. The second shaft is threaded, as indicated at 25, the threads engaging rnating threads 26 of a second mounting sleeve 27 which receives the axle 28 of inner roller 4. It will be noted that the mounting sleeve 20 for the outer roller 5 is of the size to freely surround the second drive shaft 22 and is provided with an annular bearing 29 which permits the mounting sleeve 20 to move inwardly around a portion of the second drive shaft 22. Such arrangement permits the outer roller 5 to be moved into relatively close proximity to inner roller 4; yet inner roller 4 is free to travel throughout the full extent of the second drive shaft 22 upon outward movement of the outer roller. At its innermost end, the second drive shaft 22 terminates in a beveled pinion 30 the teeth of which engage a second ring gear 31 rotatably mounted on the supporting structure 2 and concentric with the first ring gear 18.

Segments of the first and second ring gears are illustrated in FIG. 4 wherein it will be seen that the first ring gear 18 is supported by a series of bearings 32 which form an annular support about which the ring gear may be rotated. Similarly, the second ring gear 3! is supported by a series of bearings 33 which form an annular support surrounding the second ring gear. If desired, a set of bearings 34 may be interposed between the first and second ring gears; and as seen in FIG. 2, each of the ring gears may be slidably supported on bearing plates 35 and 36 mounted on the supporting structure 2. The ring gears are thus mounted for rotation and may be driven in either a clockwise or a counterclockwise direction in the manner to be described hereinafter. It will be understood, of course, that a corresponding set of first and second ring gears will be arranged to coact with the series of radially disposed drive units 3a lying on the opposite side of the device and supporting the opposite ends of the inner and outer rollers.

In the embodiment illustrated in FIG. 1, the drive units 3d and 3f are provided with synchronized reversible motors 37 and 38 connected to the outermost ends of the first drive shafts 14 of the drive units. Thus, in the case of the drive units 3d and 3f, their drive shafts 14 are driven by the motors, and the shafts in turn drive the first ring gear 18 through their pinions l7. Rotation of the first ring gear. will rotate the pinions 17 of the first drive shafts of the remaining drive units. The drive motors 37 and 38 will be synchronized to operate in unison at the same rate of speed. Separate drive motors may be provided for the drive units 30 on the opposite side of the device, or, as illustrated in FIG. 6, an opposing pair of drive units 3 and 3a may be operatively connected to a single drive motor 39 provided with suitable gearing 40 to concurrently drive the first drive shafts of he opposing drive units.

The second ring gear 31 is driven in the manner illustrated in FIG. 5, wherein a drive motor 4! is connected to a drive shaft 42 having a pinion 43 engaging the second ring gear intermediate an adjoining pair of the drive units 3. In the em bodiment illustrated in FIG. 1, a pair of drive motors 41, 41a acting through drive shafts 42 and 42a are arranged to drive opposite sides of the second ring gear. The drive motors for the second ring gear will be synchronized but will be operable independently of the drive motors for the first ring gear so that the first and second ring gears may be driven independently of each other. If desired, the drive shafts for the second ring gears lying on the opposite sides of the device may be interconnected in the same manner as illustrated in FIG. 6 in conjunction with the drive for the first ring gear.

In the operation of the device, when the first drive shafts 14 are rotated, the threaded portions 14a will cause the mounting sleeves 20 to move either inwardly or outwardly depending upon the direction of rotation, and hence the outer rollers 5 making up the outer roll cage will move accordingly, thereby either expanding or contracting the outer roll cage 7. Since the first drive shafts 14 are freely rotatable within the hollow second drive shafts 22, the rotation of the first drive shafts in no way affects the position or movement of the inner rollers 4. Rather, movement of the inner rollers 4 is controlled by the second ring gear 31 which, when rotated by the drive motors 41, 41a, acts through the pinions 30 to rotate the threaded second drive shafts 22 which, in turn, drive the mounting sleeves 27 carrying the inner rollers 4, thereby permitting the inner roll cage 6 to be expanded or contracted depending upon the direction of rotation of the second drive shafts 22. As previously indicated, there may be instances wherein it is desirable to move the outer rollers 5 into relatively close proximity to the inner rollers 4, and to this end the annular bearings 29 permit the elongated mounting sleeves 20 to move inwardly around the second drive shafts 22.

In order to protect the drive shafts and their related parts from becoming clogged with dirt and grime, it is preferred to enclose each of the drive units in a housing which, as seen in FIG. 7, may comprise opposing sidewalls 44 and 45 mounted on the supporting structure 2, the sidewalls supporting a pair of spaced-apart cover plates 46 and 47 defining a longitudinal slot 48 therebetween of a size to freely receive the axles of the yet and outer rollers, the roller 4 and axle 28 being illustrated in FIG. 7. The longitudinal slot 48is normally closed by a pair of flexible tubular members 49 and 50 which lie in edgeabutting relation. These members may be formed from rubber or plastic tubing and will be sufficiently compressible to permit the roller axles to extend between them, the tubing being compressed in the areas of the axles and yet sufficiently resilient to resume the normal tubular configuration immediately adjacent the axles. Thus, the longitudinal slots are effectively sealed against the entry of dirt and grime, and yet the axles are free to move lengthwise of the slot asthe rollers are moved in and out by the drive mechanism. The materials from which the tubular members are formed do not constitute a limitation on the invention; nor of necessity do the members have to be tubular. Rather they can be solid in cross section and of diverse configurations, provided the material from which they are formed is sufficiently resilient to permit it to be compressed by the axles.

The present invention also contemplates the provision of means for driving the rollers in the outer roll cage to facilitate the feeding of the strip as it is being accumulated. The roller drive mechanism comprises a series of interconnected roller drive units 51 overlying the rollers 5, each of the units 51 being adapted to drive a series of adjacent outer rollers 5. As will be seen in FIG. I, each of the roller drive units comprises a mounting frame 52 overlying the rollers 5 intermediate their opposite end edges. The mounting frames 52 will be pivotally mounted for movement toward and away from the roller as the rollers move inwardly and outwardly. To this end, the mounting frames may be spring biased toward their outermost positions, being drawn inwardly as the outer roll cage is caused to contract. Each of the roller drive units include a motor 53 having a drive shaft 54 which drives belt 55 passing around sheave 56 which, in turn, drives a series of. belts 57 which engage the center portions of the rollers 5a and 5b. The rollers 50 and 5b are also engaged by sets of belts 58 and 59, respectively, which lie in interdigitating relation to the belts 57, the belts 59 serving to interconnect roller 5!; with adjoining roller 5c. The belts $8, on the other hand, connect the roller 5a with the roller 50 of the next adjoining roller drive unit, so that the roller drive units are interconnected. The interdigitating relationship of the belts is illustrated in FIG. 3; and FIG. 6 illustrates that the outer rollers 5 may have reduced diameter center portions 60 to receive the belts. The multiple belts, in addition to rotating the rollers in the outer roll cage, effectively provide a continuously moving supporting surface for the strip stock as it is fed into contact with the outer roll cage; such arrangement has been found to materially assist in feeding strip into the accumulator. As should be evident. the belt drive means may take diverse forms and the arrangement illustrated is intended to be exemplary only.

As should now be apparent, the instant invention provides a compact and efficient drive means for effecting inward and outward movement of the rollers making up the inner and outer roll cages of the strip accumulator. Numerous modifications have already been set forth and others will undoubtedly occur to the skilled worker in the art upon reading this specification. For example the movement of the guide rollers may be such as to result in either circular or elliptical sets of convolutions. In the latter case, the drive shafts of the various drive units 3 may be provided with threads of differing sizes so that the relative movement of the rollers may be varied as desired. In many instances, it will be preferred that the rollers in the outer roll cage be freewheeling, in which event it is not necessary to provide means for rotating the rollers. Exemplary means have, however, been set forth for rotating the rollers in the outer roll cage. In the exemplary embodiment illustrated a plurality of rollers are driven by a single motor, it will be evident that each roller may be driven by a separate motor. While it is preferred that the ring gears lie to the inside of the drive units, it should be evident that they could be to the outside, although in many instances this would unduly increase their size and cost of manufacture.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In an accumulator for strip material having inner and outer annular roll cages each composed of a plurality of rollers arranged to support the strip as it is formed into sets of convolutions, said outer roll cage surrounding said inner roll cage and lying in spaced relation thereto, a plurality of radially disposed drive units for moving said rollers inwardly and outwardly to selectively expand and contract said roll cages, each of said drive units including first and second drive shafts, each of the rollers in said outer roll cage being operatively connected to a first drive shaft, and each of the rollers in said inner roll cage being operatively connected to a second drive shaft, said first drive shafts each being connected to a first ring gear and each of said second drive shafts being connected to a second ring gear, drive means for independently rotating said first and second ring gears, whereby rotation of either of said ring gears will cause concurrent inward or outward movement of the cage-forming rollers connected thereto.

2. The accumulator claimed in claim 1 wherein the first drive shaft of each drive unit has an inner portion and an outer portion, said outer portion being in threaded engagement with a mounting member for one end of a roller in the outer roll cage, said mounting member and roller being movable axially of said first drive shaft upon rotation thereof, the second drive shaft being hollow and surrounding the inner portion of said first drive shaft and rotatable relative thereto, a'- second mounting member for one end of a roller in the inner roll cage in threaded engagement with said second drive shaft, said second mounting member and the roller carried thereby being movable axially of said second drive shaft upon rotation thereof.

3. The accumulator claimed in claim 2 wherein said first and second ring gears are concentrically disposed with respect to each other and positioned to lie in close proximity to the inner ends of said drive units, said second drive shafts each mounting a pinion at its inner end operatively connected to the second ring gear, each of said first drive shafts projecting freely inwardly beyond the pinion on said second drive shaft and mounting a pinion operatively connected to said first ring gear.

4. The accumulator claimed in claim 3 wherein the drive means for said second ring gear comprises at least one motor operatively connected to the outermost end of at least one of said inner drive shafts.

5. The accumulator claimed in claim 3 wherein the drive means for the first ring gear comprises at least one motor having a drive shaft and pinion operatively connected to said first ring gear.

6. The accumulator claimed in claim 3 wherein the mounting member in threaded engagement with the outer portion of the first drive shaft is elongated and is of a size to freely surround a portion of said second drive shaft upon inward movement of the said mounting member.

7. The accumulator claimed in claim 3 wherein each of said drive units is enclosed in a housing having a cover facing the adjacent ends of the rollers mounted thereto, said cover having an elongated slot therein, said slot being closed by an op posing pair of compressible members lying in side-by-side, edge-contacting relation, said rollers each having an axle projecting through said slot between the said compressible members, said axles acting to compress said compressible members in the areas contacted thereby, whereby said longitudinal slot is effectively sealed against the entrance of dirt and grime into said housing.

8. The accumulator claimed in claim 3, including means operatively connected to the rollers in said outer roll cage for rotating said rollers.

9. The accumulator claimed in claim 8 wherein said rollerrotating means includes a series of interdigitating drive belts engaging the central portion at least of each of said outer rollers, said belts defining a continuously moving strip-contacting surface extending between adjoining outer rollers.

10. in an accumulator for strip material having inner and outer r011 cages each composed of a plurality of rollers arranged to support the strip as it is formed into sets of convolutions, said outer roll cage surrounding said inner roll cage and lying in spaced relation thereto, a plurality of corresponding radially disposed drive units at each end of said rollers for moving said rollers inwardly and outwardly to selectively ex pand and contract said roll cages, each end of the rollers in said outer roll cage being operatively connected to a first drive shaft, and each end of the rollers in said inner roll cage being operatively connected to a second drive shaft, the first drive shafts at each end of the rollers being jointly connected to first ring gears adjacent the corresponding ends of the rollers, and the second drive shafts at each end of the rollers being jointly connected to second ring gears adjoining the corresponding ends of the rollers, first drive means for rotating said first ring gears in timed relation, and second drive means for rotating said second ring gears in timed relation, whereby the rotation of either said first or second ring gears will cause joint movement of the cage forming rollers connected thereto.

11. The accumulator claimed in claim 10 wherein said second ring gears surround said first ring gears and are concentrically disposed with respect thereto, wherein said first drive shafts each has a pinion thereon in engagement with one of said first ring gears, and wherein said second drive shafts each has a pinion thereon in engagement with one of said second ring gears.

12. The accumulator claimed in claim 11 wherein the drive means for said first ring gears comprise at least one motor operatively connected to one of the first drive shafts at each end of said outer rollers.

13. The accumulator claimed in claim 11 wherein the drive means for said second ring gears comprises at least one motor, at each end of said rollers, said motors each being operatively connected to a drive shaft and pinion engaging said second ring gears.

14. The accumulator claimed in claim 13 wherein said second drive shafts surround at least a portion of said first drive shafts and are rotatable relative thereto, said first and second shafts each having a threaded portion in engagement with a mounting sleeve, the mounting sleeve on said first drive shaft mounting an end of an outer roller, and the mounting sleeve on the second drive shaft mounting an end of an inner roller.

15. The accumulator claimed in claim 14 wherein the mounting sleeves on said first drive shafts are elongated and of a size to in part freely surround said second drive shafts, whereby said last-named sleeves may be caused to traverse a portion at least of said second drive shafts. 

1. In an accumulator for strip material having inner and outer annular roll cages each composed of a plurality of rollers arranged to support the strip as it is formed into sets of convolutions, said outer roll cage surrounding said inner roll cage and lying in spaced relation thereto, a plurality of radially disposed drive units for moving said rollers inwardly and outwardly to selectively expand and contract said roll cages, each of said drive units including first and second drive shafts, each of the rollers in said outer roll cage being operatively connected to a first drive shaft, and each of the rollers in said inner roll cage being operatively connected to a second drive shaft, said first drive shafts each being connected to a first ring gear and each of said second drive shafts being connected to a second ring gear, drive means for independently rotating said first and second ring gears, whereby rotation of either of said ring gears will cause concurrent inward or outward movement of the cage-forming rollers connected thereto.
 2. The accumulator claimed in claim 1 wherein the first drive shaft of each drive unit has an inner portion and an outer portion, said outer portion being in threaded engagement with a mounting member for one end of a roller in the outer roll cage, said mounting member and roller being movable axially of said first drive shaft upon rotation thereof, the second drive shaft being hollow and surrounding the inner portion of said first drive shaft and rotatable relative thereto, a second mounting member for one end of a roller in the inner roll cage in threaded engagement with said second drive shaft, said second mounting member and the roller carried thereby being movable axially of said second drive shaft upon rotation thereof.
 3. The accumulator claimed in claim 2 wherein said first and second ring gears are concentrically disposed with respect to each other and positioned to lie in close proximity to the inner ends of said drive units, said second drive shafts each mounting a pinion at its inner end operatively connected to the second ring gear, each of said first drive shafts projecting freely inwardly beyond the pinion on said second drive shaft and mounting a pinion operatively connected to said first ring gear.
 4. The accumulator claimed in claim 3 wherein the drive means for said second ring gear comprises at least one motor operatively connected to the outermost end of at least one of said inner drive shafts.
 5. The accumulator claimed in claim 3 wherein the drive means for the first ring gear comprises at least one motor having a drive shaft and pinion operatively connected to said first ring gear.
 6. The accumulator claimed in claim 3 wherein the mounting member in threaded engagement with the outer portion of the first drive shaft is elongated and is of a size to freely surround a portion of said second drive shaft upon inward movement of the said mounting member.
 7. The accumulator claimed in claim 3 wherein each of said drive units is enclosed in a housing having a cover facing the adjacent ends of the rollers mounted therEto, said cover having an elongated slot therein, said slot being closed by an opposing pair of compressible members lying in side-by-side, edge-contacting relation, said rollers each having an axle projecting through said slot between the said compressible members, said axles acting to compress said compressible members in the areas contacted thereby, whereby said longitudinal slot is effectively sealed against the entrance of dirt and grime into said housing.
 8. The accumulator claimed in claim 3, including means operatively connected to the rollers in said outer roll cage for rotating said rollers.
 9. The accumulator claimed in claim 8 wherein said roller-rotating means includes a series of interdigitating drive belts engaging the central portion at least of each of said outer rollers, said belts defining a continuously moving strip-contacting surface extending between adjoining outer rollers.
 10. In an accumulator for strip material having inner and outer roll cages each composed of a plurality of rollers arranged to support the strip as it is formed into sets of convolutions, said outer roll cage surrounding said inner roll cage and lying in spaced relation thereto, a plurality of corresponding radially disposed drive units at each end of said rollers for moving said rollers inwardly and outwardly to selectively expand and contract said roll cages, each end of the rollers in said outer roll cage being operatively connected to a first drive shaft, and each end of the rollers in said inner roll cage being operatively connected to a second drive shaft, the first drive shafts at each end of the rollers being jointly connected to first ring gears adjacent the corresponding ends of the rollers, and the second drive shafts at each end of the rollers being jointly connected to second ring gears adjoining the corresponding ends of the rollers, first drive means for rotating said first ring gears in timed relation, and second drive means for rotating said second ring gears in timed relation, whereby the rotation of either said first or second ring gears will cause joint movement of the cage forming rollers connected thereto.
 11. The accumulator claimed in claim 10 wherein said second ring gears surround said first ring gears and are concentrically disposed with respect thereto, wherein said first drive shafts each has a pinion thereon in engagement with one of said first ring gears, and wherein said second drive shafts each has a pinion thereon in engagement with one of said second ring gears.
 12. The accumulator claimed in claim 11 wherein the drive means for said first ring gears comprise at least one motor operatively connected to one of the first drive shafts at each end of said outer rollers.
 13. The accumulator claimed in claim 11 wherein the drive means for said second ring gears comprises at least one motor, at each end of said rollers, said motors each being operatively connected to a drive shaft and pinion engaging said second ring gears.
 14. The accumulator claimed in claim 13 wherein said second drive shafts surround at least a portion of said first drive shafts and are rotatable relative thereto, said first and second shafts each having a threaded portion in engagement with a mounting sleeve, the mounting sleeve on said first drive shaft mounting an end of an outer roller, and the mounting sleeve on the second drive shaft mounting an end of an inner roller.
 15. The accumulator claimed in claim 14 wherein the mounting sleeves on said first drive shafts are elongated and of a size to in part freely surround said second drive shafts, whereby said last-named sleeves may be caused to traverse a portion at least of said second drive shafts. 